False-positive serological tests in acute malaria.

A range of serological tests, including rapid plasma reagin (RPR), Widal test, enzyme-linked immunosorbent assay (ELISA) for human immunodeficiency virus (HIV)-1 and -2, direct Coombs' test (DCT), and rheumatoid factor (RF) were performed in a well-characterised cohort of 100 patients with acute malaria (Plasmodium vivax infection: 31 patients; P. falciparum infection: 69 patients). Twenty-five healthy volunteers from a similar area were used as controls. Three patients from the severe P. falciparum group died, the remainder of the patients recovered completely. A large proportion of these patients showed false-positive serological reactions during the acute stage of infection, which became negative on re-testing, four weeks after recovery. In tropical countries such as India, where malaria is endemic, results of serological tests should be interpreted with caution in a patient with pyrexia of unknown origin (PUO).